Radiation process for dehydrated vegetables and fruits



United States Patent 3,484,253 RADIATION PROCESS FOR DEHYDRATED VEGETABLES AND FRUITS Clarence K. Wadsworth, Wellesley, Mass., assignor to the United States of America as represented by the Secretary of the Army a No Drawing. Filed Jan. 5, 1966, Ser. No. 519,170 Int. Cl. A231 3/26; A23b 7/02 U.S. Cl. 99-100 3 Claims ABSTRACT OF THE DISCLOSURE Irradiation with high energy ionizing radiation of dehydrated fruits and vegetables while held at temperatures below 0 C. reduces rehydration time and tenderizes said fruits and vegetables without any significant change in flavor, odor, color or texture.

This invention relates to an improved process of irradiating dehydrated vegetables and fruits which reduces rehydration time and tenderizes the irradiated items without substantially atfecting flavor, odor, color or texture thereof.

It is known to treat dehydrated vegetables with high energy, ionizing radiation, such as gamma-rays or electron beams, to reduce the rehydration time but it has been found that such irradiation imparts certain undesirable properties to the vegetables such as an undesirable change in or loss of color, loss or deterioration of flavor, development of off-odors, and excessive softening in texture.

It has been found, however, in accordance with this invention that the undesirable side effects of the high energy, ionizing radiation of dehydrated vegetables can be eliminated by irradiating the dehydrated vegetables while these vegetables are maintained .at a temperature of 0 C. or lower. The radiation dosages received by the dehydrated items will range from about 0.5 to about 12 megarads and preferably from about 1 to about megarads. Rad is a unit of absorbed dose of ionizing radiation and is equal to an energy of 100 ergs per gram of irradiated material. Suitable types of high energy, ionizing radiation for use in this invention include, for example, electron beams, gamma-rays and X-rays. Electron beams are generated by electron accelerators such as the Van de Graaf electron generator which operates at 2,000,- 000 volts with a power output of 500 watts, manufactured by the High Voltage Engineering Corp., Burlington, Mass. or the General Electric Companys 2,000,000 volt resonant transformer unit. Gamma-rays may be obtained from the decay of radioactive materials such as Cobalt 60. It is preferred, however, that the energy level of the ionice izing radiation be less than 12 million electron volts in order to avoid any induced radioactivity in the food items treated.

The dehydrated vegetables and fruits which may be treated according to this invention include, for example, cabbage, carrots, green and red bell peppers, celery, onions, leek, lima beans, okra, peas, corn, lentils, split peas, navy beans, pea beans, mushrooms, prunes, apricots, figs, peaches, pears, bananas, strawberries, papayas, raisins, dates, avocadoes, mangoes, etc. Dehydration is accomplished by any of the well-known standard commercial procedures and has as its purpose the removal of sufficient moisture from the food item so that it may be stored at ambient temperatures for extended periods of time without undergoing a loss in quality. The moisture level of the food items for purposes of this invention will 'be 20% or less by weight of the dehydrated item and preferably is less than 5% by weight.

Irradiationof the food items described in the following examples was accomplished :by exposing the food items to gamma radiation emanating from a 900,000 curie Cobalt source. The physical arrangement of the source consists of two spaced apart, parallel plaques, 42 high by 56" in length, containing the radioisotope. The samples which were packed in sealed tin cans were placed in stacked aluminum canisters and carried by a monorail conveyor between the plaques for a predetermined period of time. Ceric sulfate dosimeters were distributed throughout representative samples being irradiated to measure the dose absorbed.

EXAMPLE I Cabbage cubes, %-inch in size, were dehydrated to a moisture content of 5% by weight based. on the weight of the dehydrated cabbage and hermetically sealed in a number of tin-clad steel cans. Half of the total number of cans of dehydrated cabagge cubes so prepared were chilled by immersion in liquid nitrogen and while at a temperature of approximately -:5 C. were exposed to gamma radiation as hereinbefore described at various dosage levels. The other half of the total sample of cans were irradiated at ambient temperatures Within the radiation chamber which ranged from about 30 C. to more than 72 C. The low temperature irradiated cabbage was compared with the ambient temperature irradiated cabbage and the results set forth in Table I.

The evaluation was made in this example by a panel of experienced food testers using a 9 point scale wherein 9 is the highest score and 1 is the lowest score. Rehydration of the control was accomplished by combining the cabbage with an excess of cold water (15 C.) and holding at room temperature for 45 minutes, the time required to rehydrate the control. Rehydration times for the other samples was reduced as indicated in Table I.

TABLE I Rehydration Color Odor Flavor Texture Appearance time (111111.)

7. 1 6. 3 5. 4 4. 9 6. 4 25 5. 7 5. 3 4. 4 3. 7 5.1 12 Badly discolored, substandard odor, appearance, flavor Discarded Same as 6 Discarded From the foregoing results, it can be seen that dehydrated cabbage which was irradiated to a dosage level of 2 megarads at -180 :5 C. rehydrates in less than one-half the time required by the non-irradiated control and gave a product which was essentialy comparable in color, odor, flavor, texture and appearance to the control. On the other hand, the sample irradiated to the same dose level at ambient temperatures was significantly poorer in flavor and texture. The differences between the ambient and low temperature irradiated samples becomes greater with increasing dosages which cause color, odor and appearance of the ambient samples to fall far below those of the low temperature treated samples. These data clearly show a significant advantage for low temperature irradiation of the dehydrated product.

EXAMPLES II Red bell peppers, cut into sections approximately A" X x A", were dehydrated to a moisture content below 6% by weight based on the weight of the dehydrated peppers and hermetically sealed in tin-clad steel cans. These dehydrated peppers had a specific gravity of 0.34. The cans of dried peppers were subsequently irradiated with various doses of gamma radiation from the Cobalt 60 source as described in Example I. One-half of the total sample of cans of dried peppers was irradiated at ambient temperatures, and the remaining portion of the sample was irradiated at a temperature of approximately -l80 :5 C. Rehydration was accomplished by combining the peppers with an excess of cold water which was brought to a temperature of 100 C. and held at this temperature for two minutes. An evaluation of the samples was made by a panel of seven experienced food testers. A nine point scale was employed for purposes of evalu= ation, with 9 being the highest possible score and 1 being the lowest score. The results of the panel evaluation of the rehydrated peppers irradiated at ambient, and low temperatures and a control unirradiated sample are set forth below in Table II.

The results indicate that at both dosage levels the low temperature irradiated product is markedly superior to the ambient temperature irradiated product in odor, flavor and texture and at 6 mrads indicates an improvement in color and appearance.

EXAMPLE III Green peppers cut into approximately fir-inch cubes were dehydrated to a moisture content below 5% by weight based on the weight of the dried peppers and hermetically sealed in steel cans. The dried product has a specific gravity of 0.22. A sample portion of the cans of the dried peppers was irradiated as in Example II at ambient temperatures and another sample portion was irradiated at low temperatures and evaluated as in Example II. The results of the evaluaiton are set forth below in Table III.

TABLE III Temp. Appear- Dose 0.) Color Odor Flavor Texture mice The evaluation scores reported in Table III indicate that low temperature irradiation results in a rehydrated product that is superior to the ambient temperature irradiated rehydrated product. At a dose level of 4 mrads the low temperature irradiated product is quite similar to the unirradiated control and rehydrates in less than one-half the time required for the control. The difference in scores between the ambient and low temperature irradiated peppers is especially significant in terms of flavor and texture.

It will be understood that the above-described embodiments of the invention are illustrative only and that modifications will occur to those skilled in the art. The invention is therefore not to be limited to the specific examples disclosed herein but is to be defined by the claims.

I claim:

:1. A method of processing fruits and vegetables, other than potatoes, so as to tenderize the same and reduce the time required to rehydrate said fruits and vegetables, which method comprises:

(a) dehydrating said fruits and vegetables to a moisture content of less than 20% by weight,

(b) lowering the temperature of said dehydrated fruits and vegetables to l 15 C.,

(c) irradiating said dehydrated fruits and vegetables while held at -l80 :5" C. with a source of high energy ionizing radiation to a dose within the range of 2.0 megarads to 12 megarads.

2. A method according to claim 1 wherein the moisture content of said fruits and vegetables is dehydrated to a moisture content of less than 5% by weight.

3. A method according to claim 2 wherein said dehydrated fruits and vegetables are irradiated to a dose of from about 4 to about 10 megarads.

References Cited UNITED STATES PATENTS 2/ 1961 Baldwin 99-217 3/1962 Schroeder 99-100 XR US. Cl. X.R. 99204, 217 

